1. Field of the Invention
The present invention relates to motors for washing machines, and more particularly, a direct coupling type motor for a washing machine, which is directly coupled to a drum of the washing machine, for rotating the drum.
2. Discussion of the Related Art
A rotor of a related art motor for the washing machine which is entirely injection molded of plastic, requires a complicated mold and fabrication process, and is liable to shrinkage during cooling of the injection molded plastic, thereby being unable to obtain an original shape.
FIG. 1 illustrates a section of a rotor of a motor of a related art washing machine.
Referring to FIG. 1, the related art rotor is provided with a rotor frame 1 of injection molded plastic which forms an exterior of the rotor, magnets 3 secured to an inside surface of an outer edge of the rotor frame 1, each with an N-pole and an S-pole arranged alternately, a back yoke 2 on an outer side of the magnets 3 for forming a flux path, heat dissipation frames 7 formed as one body with the rotor frame 1 on an underside thereof for forced movement of air to cool the motor, a driving shaft 5 inserted in a pass through hole in a central portion of the rotor frame 1, a serration 4 at a portion where the driving shaft 5 and the rotor frame 1 come into contact for secure rotation of the driving shaft 5, a fastening bolt 6 inserted in and fastened to the driving shaft 5, and reinforcing ribs 8 projecting from an upper side and/or a lower side of the rotor frame 1, for reinforcing the rotor frame 1.
The plastic rotor of the related art washing machine has a hazard in that the rotor is liable to deform by an external impact. Also, the complicated rotor shape complicates the mold used for injection molding, thereby making injection molding difficult.
Moreover, since the injection molded plastic may undergo deformation after the injection molding, an injection molded body is liable to have a shape different from a desired shape. If fabrication of the rotor frame 1 to exact dimensions fails due to deformation that occurs during the injection molding process, particularly, a cooling process, the rotor frame 1 causes interference with other parts, such as a stator of the motor, thereby potentially causing the inoperability of a washing machine which uses these parts.
If the plastic is flexible, the rotor frame 1 may be deformed by external force which may occur during operation of the washing machine, and interfere with other parts, thereby potentially causing the inoperability of a washing machine inoperative which uses these parts.